Principled observance declared? (5)
I believe the answer is:
right
'principled' is the definition.
(thesaurus)
'observance declared?' is the wordplay.
'observance' becomes 'rite' (I've seen this in another clue).
'declared?' indicates a 'sounds like' (homophone) clue.
'rite' sounds like 'RIGHT'.
(Other definitions for right that I've seen before include "Genuine" , "Properly" , "Due" , "Just - correct - title" , "''The customer is always .....''" .)